Autosomal dominant polycystic kidney disease (ADPKD)is a major cause of disabling morbidity and is the fourth leading cause of end-stage renal failure in the world, affecting more than 500,000 U.S. citizens and millions more worldwide. Researchers at the University of Alabama, Emory University, University of Kansas, Mayo Clinic and Washington University St. Louis joined together in 2000 to create the Consortiumfor Radiologic Studies of Polycystic Kidney Disease (CRISPI). The primary objectives of this investigation were to: (1) to develop and test the accuracy and reproducibility of imaging techniques to monitor changes in renal cyst size and parenchyma! involvement, (2) to establish and maintain a database of uniformly and accurately collected information, and (3) to maintain and make available such data to facilitate the planning and implementation of clinically appropriate interventions in the near future. The goals of CRISPII are to extend the observations of CRISPI in order to: 1) draw unequivocal linkage between the rate of kidney/cyst enlargement and qualitative and quantitative end-points; 2) to provide a marker of disease progression (kidney volume) sensitive and accurate enough to be used as a primary outcome marker in clinical trials aiming to forestall disease progression; 3) to develop and test other biomarkersof disease progression in ADPKD. The specific aims are: Aim 1: Extend the preliminary observations of CRISPIto ascertain the extent to which quantitative (kidney volume and hepatic and kidney cyst volume) or qualitative (cyst distribution and character) structural parameters predict renal insufficiency. Aim 2: Extend the preliminary observations of CRISP! to ascertain the extentto which age and sex-adjusted measurements of renal blood flow byMR technology predict the rate of renal growth; and, renal blood flow and kidney volume predict the rate of renal function decline in ADPKD.Aim 3: Exhaustively analyze the living database and stored biologic samples derived from CRISPI and the CRISPII extension to develop and test new metrics to quantify and monitor disease progression. Given that hypertension appears to be a predictor of greater rates of renal and cyst growth during CRISP I, in CRISP II we will obtain ambulatory blood pressure data on normotensiveCRISP II participants and continue to collect circulatory markers of the renin-angiotensin-aldosterone system (plasma renin activity, plasma aldosterone concentration and urinary aldosterone excretions) in all CRISPII participants.